This invention generally relates to material transport systems and more particularly to a granular semiconductor material transport system capable of continuous, non-contaminating transfer of granular semiconductor material from a large source vessel to a smaller and more manageable target vessel by flowing transfer fluid, without complicated transfer apparatus.
The invention is especially concerned with a material transport system capable of efficiently moving large quantities of granular semiconductor material, such as polysilicon, while reducing contamination of the granular material as it passes through the system. Systems for moving particulate matter are well known in the art. Conventionally, particulate matter transfer systems transfer particulate matter, such as grain, or synthetic particulate matter used for injection molding. These systems often use a moving fluid, such as air, to transfer particulate matter through the system. These systems are not ideal for all applications, however, because the conduits are typically formed from materials different from the particulate matter flowing through the conduit. Over time, these conduits wear, adding unwanted contaminants to the particulate matter. Such contamination is acceptable for some applications, but not with granular semiconductor material.
For granular semiconductor material, no appropriate transport system exists and other challenges remain unaddressed. Before processing, granular semiconductor material is typically stored in large, shipping vessels, or source vessels. Such vessels are cumbersome to empty and typically must be lifted and inverted, allowing the granular material to flow from the vessel by gravity. Constructing an apparatus large enough to lift and invert such a vessel is difficult. Moreover, this difficult operation presents safety, ergonomic and facility space concerns. In addition, because the size and shape of such source vessels vary widely, constructing a lifting and inverting machine that will work with all vessels is difficult. As such, a better method for removing the granular polysilicon from the source vessel is needed, where the source vessel need not be lifted or inverted to remove the contents and the size and shape of the source vessel is immaterial.
Among the several objects and features of the present invention may be noted the provision of a granular semiconductor material transport system which decreases the potential for contaminating the granular polysilicon during transfer; the provision of such a system which contains the material within the system without allowing material to exit the system or for foreign matter to contaminate the material; the provision of such a system which removes dust from the granular material; the provision of such a system which controls material flow with sufficient precision to transfer precise amounts of material; the provision of such a system which is safe to operate; and the provision of such a system which can move a large amount of material cost effectively and efficiently.
Generally, a granular semiconductor material transport system of the present invention for transporting granular polysilicon comprises a feed tube having one end in fluid communication with a granular polysilicon supply. The feed tube transfers a transfer fluid to the supply and transfers granular material entrained in the transfer fluid from the supply. One end of the feed tube further comprises an outer tube and an inner tube. The outer and inner tubes are arranged to form an annular cavity between the inner and outer tubes. The annular cavity defines a passage for transferring the transfer fluid from a fluid supply to the granular polysilicon supply. The interior of the inner tube transfers the transfer fluid entrained with granular material from the granular polysilicon supply. A process vessel sealably receives an opposite end of the inner tube for receiving transfer fluid entrained with granular material into the process vessel. A vacuum source sealably connects to the process vessel to evacuate the process vessel and remove dust-entrained transfer fluid from the process vessel.
In another aspect of the present invention, a granular material transport system comprises a supply of transfer fluid and a mover in fluid communication with the supply of transfer fluid for drawing the transfer fluid from the supply and creating a flow of said transfer fluid. The system further comprises a process vessel in fluid communication with a granular material supply for receiving the transfer fluid flow entrained with granular material and processing the fluid to separate the granular material from the transfer fluid and any dust. A transfer fluid processing apparatus in fluid communication with the process vessel removes any residual granular material and dust from the transfer fluid. The apparatus is in fluid communication with the mover for returning the treated transfer fluid to the system.
In yet another aspect of the present invention, a process is disclosed for transporting granular semiconductor material in a contaminant-free environment. The process comprises steps of bringing a bulk supply of granular polysilicon at a first location into fluid communication with a location of lower pressure to induce movement of the granular polysilicon toward the location of lower pressure. The process further comprises dedusting the granular polysilicon as it moves toward the location of lower pressure and delivering the dedusted granular polysilicon to a second location.
Other objects and features will be in part apparent and in part pointed out hereinafter.